Energy metabolism of Brahman × Friesian and Friesian calves, and the influence of an increase in rectal temperature on their heat production

Abstract

The energy metabolism of five Friesian and five Brahman × Friesian calves was measured at 15°c, at two levels of feeding on a diet of hay and pellets; measurements were also made on another three calves of each breed at the lower level of feeding. The results showed that differences between breed types were very small, although the crossbred calves produced significantly less methane than the Friesians. Values of 0.43 and 0.44 MJ ME/kg^0.75 daily were calculated for the metabolisable energy (ME) required for maintenance; the calculated values for the net efficiency with which ME was utilised above maintenance (kg) were 0.51 and 0.54. The heat production of some of the calves, fed on a maintenance level of feeding, was measured at an air temperature of 18°–25°c and at a higher temperature which was sufficiently high to cause rectal temperature to increase by 1–2°c. Heat production was generally higher in association with the elevated rectal temperature; however, there appeared to be no differences in this respect between the breed types, nor between calves which had previously been kept at a high or at a low temperature.